Inorganic fillers are frequently used to make polymers flame retardant. However, the levels of inorganic fillers required to impart sufficient flame retardancy to the polymers result in difficult processing. Moreover, many of these fillers are mineral hydrates. Such mineral hydrates can react with moisture curable resins during storage which limits the shelf life of such resins.
The approach of loading the fillers into a masterbatch that is then coextruded with a moisture curable resin has been used to provide a moisture curable composition capable of being used to meet automotive wiring applications. This approach mitigated storage stability issues of moisture curable resin and hydrated mineral tiller compositions which prematurely crosslink. One problem with the masterbatch approach was the ability to achieve sufficient flame retardancy while still having sufficient crosslinking. The crosslinking is limited by the amount of moisture curable resin that is added to the composition. However, coextrusion with higher amounts of moisture curable resin lowers the amount of flame retardant in the final composition.
Accordingly, a moisture curable resin having high filler content and easy processability was still needed, particularly for applications requiring flame retardant polymers, such as automotive wires and cables.